全文获取类型
收费全文 | 236054篇 |
免费 | 17099篇 |
国内免费 | 11585篇 |
专业分类
化学 | 121886篇 |
晶体学 | 2541篇 |
力学 | 16150篇 |
综合类 | 621篇 |
数学 | 50710篇 |
物理学 | 72830篇 |
出版年
2023年 | 2051篇 |
2022年 | 2679篇 |
2021年 | 4173篇 |
2020年 | 4974篇 |
2019年 | 4990篇 |
2018年 | 14558篇 |
2017年 | 14252篇 |
2016年 | 12124篇 |
2015年 | 6096篇 |
2014年 | 7300篇 |
2013年 | 9836篇 |
2012年 | 14500篇 |
2011年 | 21384篇 |
2010年 | 13662篇 |
2009年 | 13796篇 |
2008年 | 14909篇 |
2007年 | 16312篇 |
2006年 | 7515篇 |
2005年 | 7530篇 |
2004年 | 6736篇 |
2003年 | 6392篇 |
2002年 | 5440篇 |
2001年 | 4159篇 |
2000年 | 3560篇 |
1999年 | 3190篇 |
1998年 | 2939篇 |
1997年 | 2689篇 |
1996年 | 2696篇 |
1995年 | 2189篇 |
1994年 | 2106篇 |
1993年 | 1908篇 |
1992年 | 1746篇 |
1991年 | 1730篇 |
1990年 | 1635篇 |
1989年 | 1448篇 |
1988年 | 1284篇 |
1987年 | 1215篇 |
1986年 | 1158篇 |
1985年 | 1147篇 |
1984年 | 1091篇 |
1983年 | 946篇 |
1982年 | 912篇 |
1981年 | 798篇 |
1979年 | 873篇 |
1978年 | 873篇 |
1977年 | 863篇 |
1976年 | 963篇 |
1975年 | 850篇 |
1974年 | 866篇 |
1973年 | 896篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
曾六川 《高校应用数学学报(英文版)》2003,18(3):283-286
Let(X,‖·‖ ) be a Banach space.Let K be a nonempty closed,convex subset of Xand T∶K→K.Assume that T is Lipschitzian,i.e.there exists L>0 such that‖ T(x) -T(y)‖≤ L‖ x -y‖for all x,y∈K.Withoutloss of generality,assume that L≥ 1 .Assume also that T is strictly pseudocontractive.According to[1 ] this may be statedas:there exists k∈ (0 ,1 ) such that‖ x -y‖≤‖ x -y + r[(I -T -k I) x -(I -T -k I) y]‖for all r>0 and all x,y∈ K.Throughout,let N denote the set of positive in… 相似文献
992.
993.
994.
The periodic precipitation pattern formation in gelatinous media is interpreted as a moving boundary problem. The time law,
spacing law and width law are revisited on the basis of the new scenario. The explicit dependence of the geometric structure
on the initial concentrations of the reactants is derived. Matalon—Packter law, which relates the spacing coefficient with
the initial concentrations is reformulated removing many ambiguities and impractical parameters. Experimental results are
discussed to establish the significance of moving boundary concept in the diffusion controlled pattern forming systems 相似文献
995.
The rotational spectra of three low-energy conformers of thiodiglycol (TDG) (HOCH2CH2SCH2CH2OH) have been measured in a molecular beam using a pulsed-nozzle Fourier-transform microwave spectrometer. To determine the likely conformational structures with ab initio approach, conformational structures of 2-(ethylthio)ethanol (HOEES) (CH3CH2SCH2CH2OH) were used as starting points together with the consideration of possible intramolecular hydrogen bonding in TDG. Three lower-energy conformers have been found for TDG at the MP2=Full/6311G** level and ab initio results agree nicely with experimentally determined rotational constants. In addition, Stark measurements were performed for two of the three conformers for dipole moment determinations, adding to our confidence of the conformational structure matches between experimental observations and ab initio calculations. Of the three lower-energy conformers, one displays a compact folded-like structure with strong hydrogen bonding between the two hydroxyl groups and the central sulfide atom. Two other conformers have relatively open chain-like structures with hydrogen bonding between each of the hydroxyl groups to the central sulfur atom, of which one has pure b-type dipole moment according to the ab initio results. 相似文献
996.
Computer processing of electronic absorption spectra of rare-earth elements in inorganic laser media
Algorithms and program modules are developed for calculation of the Judd-Ofelt parameters on modern computers. These programs can be used to perform numerical analysis of the energy absorption by rareearth ions in laser media. 相似文献
997.
The rate-dependent effects in metallic ferromagnetic materials with magnetization processes attributed to domain-walls motion were studied. The experimental method for eddy-current relaxation time determination was proposed. Some discrepancies between the data and theoretical predictions were observed and discussed. The origin of these discrepancies is accounted for by the decrease of viscous-type relaxation process as the rate of change of averaged magnetization is approaching zero. 相似文献
998.
999.
Simple Entanglement Measure for Multipartite Pure States 总被引:3,自引:0,他引:3
Feng Pan Feng Pan Feng Pan Dan Liu Guoying Lu J. P. Draayer 《International Journal of Theoretical Physics》2004,43(5):1241-1247
A simple entanglement measure for multipartite pure states is formulated based on the partial entropy of a series of reduced density matrices. Use of the proposed new measure to distinguish disentangled, partially entangled, and maximally entangled multipartite pure states is illustrated. 相似文献
1000.
The Nambu-bracket quantization of the hydrogen atom is worked out as an illustration of the general method. The dynamics of topological open branes is controlled classically by Nambu brackets. Such branes then may be quantized through the consistent quantization of the underlying Nambu brackets: properly defined, the quantum Nambu-brackets comprise an associative structure, although the naive derivation property is mooted through operator entwinement. For superintegrable systems, such as the hydrogen atom, the results coincide with those furnished by Hamiltonian quantization - but the method is not limited to Hamiltonian systems. 相似文献